/Engine/Source/Runtime/GeometryCore/Public/DynamicMesh/MeshTangents.h
Calculate per-triangle tangents and then projected to overlay normals at each triangle-vertex
void ComputeSeparatePerTriangleTangents ( const [FDynamicMeshNormalOverlay](API\Runtime\GeometryCore\DynamicMesh\FDynamicMeshNormalOverlay) * NormalOverlay, const [FDynamicMeshUVOverlay](API\Runtime\GeometryCore\DynamicMesh\FDynamicMeshUVOverlay) * UVOverlay, const [FComputeTangentsOptions](API\Runtime\GeometryCore\DynamicMesh\FComputeTangentsOptions) & Options )